Brake mechanism



Nov. 10, 1936. G. L. SMITH BRAKE MECHANISM Filed April '7, 1956 Patented Nov. 10, 1936 2,060,429 BRAKE MECHANISM George L. Smith, Washington, D. 0., assignor to Thermo rakes Corporation,

Washington,

D. 0., a corporation of Virginia Application April '7, 1936, Serial No. 73,148 8 Claims, (Cl. 188-795) My invention relates to automatic adjusting mechanism for brakes on motor vehicles and is especially adaptable to hydraulically operated brakes in which any slight variations in the running clearance of the several brakes is compensated for by the flow of liquid from one operating cylinder to another as necessary to produce equal brake applying pressure on all brakes. It is illustrated for use on a well known duoservo type of hydraulic brake in which the ad lusting mechanism constitutes a floating connection between the primary and secondary shoes, and includes a theme sensitive ratchet lever similar to that shown in my Patent No.

10 2,019,101 of October 29, 1935 for Automatic brake mechanism for vehicles.

The object of my invention is to maintain the running clearance of the brake practically constant regardless of wear of the brake lining and also to keep this clearance about constant around the entire circumference of the brake so that there will be no dragging of the brakes at any ime.

In the drawing chosen to illustrate my invention the scope whereof is set forth in the appended claims:

Figure 1 is a side elevation partly broken away of a brake mechanism embodying my invention; and

Figure -2, a' view partly in section of the ,adjuste ing link connecting the two shoes of the brake.

Referring to the drawing the complete brake shoe is composed of the primary shoe P and the secondary shoe S, both of which anchor on the post Ill carried by a suitable backing plate II. This plate ll also carries an hydraulic cylinder l2 of the well known type for expanding the shoes into engagement with the drum D.

, The two shoes are connected by an adjusting mechanism consisting of a screw threaded clevis bolt l3 secured to the web of shoe S by the pin l5. This bolt is threaded into a sleeve l6 which is provided with a ratchet wheel I! at its left end. The leftend of this sleeve I6 has a socket with its center in line with the plane of the ratchet wheel II, which socket receives a ball 18 on the end of a fitting l9 rigid- 1y clamped to" the web 20 of shoe P by a bolt 2|. My preferred construction of this joint is to crimp the metal of the socket around ball ill to form a permanent connection between sleeve l6 and fitting I9.

The bolt 2| has an extension 2| forming a pivot upon which the ratchet pawl 22 is mounted and this pawl has a l'zp 23 engaging the teeth of the ratchet wheel II. A stud 24 mounted on the fitting l9 limits the upward movement of the pawl 22 and a torsion spring 25 mounted on the extension to the bolt 2| acts to rotate the pawl against this stud 24. 5

A thermo-sensitive lever arm 26 is secured to the pawl 22 by rivets 21 and is located as close to the braking surface of the drum as possible without touching it, to ensure rapid transmission of heat fromthe brake drum D to this lever 10 arm when the former becomes hot. The metal of the arm next the drum is aluminum or some other metal having a high co-eflicient' of expansion, and that next the pawl is steel, so that a rise in temperature of this thermo-sensitive arm 15 26 will bend its end 28 upward.

To operate the ratchet pawl a link 29 is connected to the anchor stud l0 and to one arm of a bell crank lever 30 pivoted at 3l'to the web 20 of the shoe P. The other arm of this lever is 2 connected to the end 28 by a link 32 having a, hemispherical button 32a atits lower end which bears against the under side of the hole in end 28 through which the link 32 passes.

A lip 22a is bent out from the body of ratchet 25 pawl 22, passes through a slot 26a in the left lend of the arm 26 and bears upon the under side \of the button 32a. This permits the brake release spring 45 to assist the spring 25 in rotating the pawl 22 to its initial position after it has 30 picked up a tooth on wheel IT, as follows:

When brake is released after application, the J shoe P swings clockwise and again contacts the anchor post l0, During this movement a downward thrust is developed in link 32 due to the counter-clockwise pivoting of bell-crank 30 about pivot 3|. Thus the button 320 presses down on lip 22a and rotates the pawl 22 counterclockwise. In addition to permitting the above action, the lip 22a also serves as a guide for the 40 .left end of the thermo-sensitive arm 26, which,

being relatively long, might otherwise be accidentally bent out of place.

l The mechanism operates as follows:, Whenthe brake is applied through the instrumentality of the cylinder l2 to arrest forward movement of the vehicle, the shoe S anchors on the post l0 and the shoe P moves away from it, opening up a gap therebetween. This causes a clockwise ro- 5o tation of the bell-crank 30, as the pivot 3| moves 7 the brake lining 33. Also the end 28 of the action of the connections between anchor thermo-sensitive arm 25 will bend upward and away from the button 32a as the brake becomes.

hot, thus introducing lost motion which will render the link 32 less effective in its action of rotating the pawl 22, and overadjustment of the brake when hot will be avoided. It will also be noted that with link 29 connected to the center of the anchor pin I 0 any pivoting of shoe P about this anchor, as the brake is expanded in its adjustment for wear, will have no effect upon the ID and pawl 22.

While the above mechanism will act to automatically maintain a constant running clearance at all times, it will not center the shoes to keep them from swinging about the post l0, and dragging against the brake drum D either on one side or the other. This action is prevented by the clearance adjuster A as follows:

A pivot 34 is secured to the backing plate II and on it is mounted a ratchet lever 35 having a circular portion 36 which is eccentric to the pivot 34. A flange 31 is turned down on web l4 forming with the cylindrical part 38 of the shoe S a channel slightly wider than the diameter of the portion 36. The arm 39 of ratchet lever 35 is fitted at its outer end with a spring pawl 40 which engages the ratchet teeth of a rack 4| secured-to the backing plate H by rivets 42. A spring 43 connects the web l4 with a stud 44 on backing plate to keep the cylindrical part 38 of shoe bear- 4 ing against portion 36 of lever 35 when brake is released.

This adjuster operates as follows: When the brake is applied the shoe S swings outward about post l0 toward the brake drum D carrying flange 31 with it. If wear of the lining 33 is sufficiently great, this outward movement will cause flange 31 to press against portion 36 and exert a rotary force on ratchet lever 35 to swing its short arm outward and its long arm 39 inward until pawl 40 picks up a new tooth on rack 4|. As portion 36 is now moved farther away from the brake center, the shoe S, when brake is released, will be held closer to the brake drum and the clearance at this point will be equal to the difference between the width of channel 31, 38 and the diameter of the portion 36. v

I claim:

1. In a brake mechanism, a brake anchor, a

brake shoe having brake applying movement shoes, and a thermo-sensltive adjusting mechanism for said link mounted on one of said shoes and connected to said anchor.

4. In an automatically adjustable brake, a pair of brake shoes, 9. floating connecting link between adjacent ends of said shoes having a ratchet wheel, and a thermosensitive ratchet lever pivotally mounted on one of said shoes and engaging said ratchet wheel.

5. In a brake mechanism, a brake anchor, a pair of brake shoes having brake applying movement away from said anchor, an adjustable connecting link between said shoes having a ratchet wheel and thermo-sensitive operating means for adjusting said link, said means interconnecting said ratchet wheel with said anchor.

6. In a brake mechanism, an anchor, brake shoes movable with respect to said anchor and having an adjustable connection, and operating means secured to said anchor and engaging said connection to adjust it.

7. In a brake mechanism, an anchor, primary and secondary brake shoes engaging said anchor and having brake applying movement with respect thereto, an adjustable connection between adjacent ends of said shoes, and operating means for said connection mounted on the primary shoe and connected to said anchor.

8. In an automatically adjustable brake, a brake anchor, a painof brake shoes, a floating adjustable link connecting adjacent ends of said shoes, and an adjusting mechanism engaging said link mounted on supports carried by and adjacent the ends of one shoe and connected to said anchor.

GEORGE L. SMI'I'HI. 

